1. Technical Field
The present invention relates to a video signal processing integrated circuit (IC) and an IC designing method and, more particularly, to a method for designing an envelope detecting circuit for a video signal processing IC in order to reduce operating steps and material costs by minimizing the number of components of external application circuits of the video signal processing IC, and to an IC using the method.
2. Related Art
In general, in order to execute auto tracking in a video cassette recorder (VCR), an envelope of a frequency modulated (FM) video signal is detected during a playback mode for input to a microprocessor, which is also called a μ-COM. Then, the microprocessor executes auto tracking control using the waveform level of the input envelope.
However, a problem arises in that the level of the input envelope differs according to the playback mode. That is, in the super long playback (SLP) mode, the width of a video track recorded on a video tape is relatively narrow, whereas in the standard playback (SP) mode, the width of the video track is relatively wider. Accordingly, the level of the detected FM video signal is relatively low in the SLP mode. Thus, in order to execute auto tracking accurately, irrespective of the playback mode, it is necessary to reduce the variation in the envelope level with the type of playback mode.
As a result of the above phenomenon, it is necessary to maintain the envelope level at the same level according to the playback mode, and this has only been possible up to this point by increasing the number of peripheral components of the video signal processing IC, resulting in a lowering of the manufacturing efficiency and an increase in material cost.